A 48-year-old married female born out of a non-consanguineous marriage presented to us with complaints of multiple raised, gradually itchy progressive lesions over her body for the past 30 years. There was no similar involvement in her siblings and parents. On cutaneous examination, multiple skin colored to hyperpigmented crusted follicular papules were present on her face, V areas of the chest, back, bilateral upper limbs and lowers limbs [Figure 1]. Biopsy performed from the papular lesions revealed the classic features of Darier’s disease viz. suprabasal clefts, dyskeratotic “corp ronds” and “grains” [Figure 2]. After the clinical and histological findings, she was diagnosed as a case of Darier’s disease.

On further query, the patient gave the family history of similar involvement in three out of her four daughters. Her daughters were of 21, 17 and 12 years old. They were born of non-consanguineous marriage. On physical examination of her daughters, the classical lesions of Darier’s disease were present, though in a less severe form. The second daughter of the proband however, showed besides these, a pigmented nevus and a flat hypopigmented lesion over the left shoulder and left forearm. The pigmented nevus was 1.5 cm × 3.5 cm oval greyish palpable plaque with presence of vellus hair over it. Adjacent to it was another 1.5 cm × 2 cm oval brownish macule with dark grayish spots over it. These lesions were clinically of a medium sized congenital melanocytic nevus (CMN) with satellites at the periphery. The lesions were present since birth. They were in a linear and blashkoid pattern. A hypopigmented interrupted but grouped macule, which was arranged in a curvilinear pattern, extending from the left scapular region to the left mid-arm of dimension 4 cm × 13 cm with irregular well-defined serrated margins, not extending to the midline, was present too [Figure 3]. Diascopy test on the hypopigmented spot was negative. Wood’s lamp examination also showed an off white color. On the basis of this, a diagnosis of segmental nevus depigmentosus was made. There were no preceding fluid-filled or raised palpable lesions prior to it. These lesions have been present since birth with a gradual proportionate increase in size, but they have been stable for the last 1 year. They also tend to follow the lines of blashko. There were no other systemic complaints in the second daughter, nor any other developmental abnormalities were found. The biopsy couldn’t be done as the daughter was only 17 years old and the mother didn’t give the consent. On the basis of the history and clinical examination, the daughter was diagnosed as a case of Darier’s disease with CMN and nevus depigmentosus. Topical tazarotene 0.1% gel was given in a short contact therapy for the daughter. There was some improvement in her skin lesion as well. She later discontinued after using it for 1 month.

Figure 3: Medium sized congenital melanocytic nevus (CMN) with satellites at the periphery and adjacent nevus depigmentosus over the left shoulder and left arm

Although nevus depigmentosus and CMN occur commonly, their coexistence in a pattern of allelic twin spotting has not been previously reported.

Twin spots or didymoses refer to the occurrence of two different nevi or paired patches of structurally or functionally different mutant tissue that differ from the surrounding normal skin. They may be present adjacent to one another or on contralateral sides. They are due to early post-zygotic mutation or loss of heterozygosity. They probably reflect different recessive mutations on the same gene locus on either pair of homologous chromosomes post-mitotic crossover. Two or more nevi that originate from the same type of cell are referred to as allelic twin spots and if they originate from different types are referred to as non-allelic twin spots.[1],[2] In our patient, nevus depigmentosus and CMN were present on the same side in a linear pattern. Because both conditions arise due to the disturbances of melanocytes, we can consider it as allelic twin spots. Nevus depigmentosus has presented as twin spotting with segmental lentiginosis as well as with Becker’s nevus.[3],[4],[5] However, this presentation of nevus depigmentosus along with CMN is an example of twin spotting which has not been reported previously. Though the occurrence of Darier’s disease with twin spotting can occur by chance, it has not been reported to the best of our knowledge.

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